1. Field of the Invention
The present invention relates to a digital video effects generators, and in particular, to read-side digital video effects generators.
2. Description of the Related Art
Digital video effects systems, including digital video effect generators and video combiners, are well known and widely used in the art. Generally, a digital video effects system receives at least two video input signals, with one selected for use as a video fill signal and the other selected for use as a video background signal. This selection involves another input signal, i.e. a key signal, which selectively keys the fill video over the background video. If the video input signals are digital, they are typically in accordance with the SMPTE D1 standard. However, sometimes one or more of the input signals may be in accordance with the SMPTE D2 standard, thereby requiring conversion to the SMPTE D1 standard. These video signals can then be processed in accordance with a number of well known video effects. For example, the fill video can be keyed onto the background video with perspective or rotational effects, or a video image can be constructed which appears to be a three-dimensional object with fill video occupying the faces of the object. While all of the foregoing, and much more, can be achieved with conventional digital video effects systems, many limitations have existed.
A problem with conventional systems involves the use and storage of keyframes within effects memories. An effect is constructed from one or more keyframes. The keyframes record various parametric data reflecting the status of the effects machine at a particular point in time. When an effect is run, the parametric data between keyframes can be smoothly interpolated or splined. Multiple effects can be stored in the effects machine at one time. However, a major limitation is the inability to smoothly transition between different effects. Conventional systems have required manual addition of a second effect's keyframes to the keyframe list of a first effect. This takes a great deal of time, and can often cause the effect. keyframe storage limits to be exceeded.
Another problem with conventional systems involves the interpolation of motion of an image between keyframes. This is a problem in particular when "corner pinning" is involved. Interpolated motion imparted to the video images between keyframes produces images having undulating, swelling and contracting dimensions, i.e. image corners which do not remain "pinned" between keyframes.